.\" Copyright (c) 2011 Kai Wang
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.\" $Id: dwarf_expand_frame_instructions.3 3962 2022-03-12 15:56:10Z jkoshy $
.\"
.Dd November 9, 2011
.Dt DWARF_EXPAND_FRAME_INSTRUCTIONS 3
.Os
.Sh NAME
.Nm dwarf_expand_frame_instructions
.Nd expand frame instructions
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_expand_frame_instructions
.Fa "Dwarf_Cie cie"
.Fa "Dwarf_Ptr instructions"
.Fa "Dwarf_Unsigned len"
.Fa "Dwarf_Frame_Op **ret_ops"
.Fa "Dwarf_Signed *ret_opcnt"
.Fa "Dwarf_Error *error"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_expand_frame_instructions
translates DWARF frame instruction bytes into an array of
.Vt Dwarf_Frame_Op
descriptors.
.Pp
Argument
.Fa cie
should reference the CIE descriptor associated with the instructions
to be translated.
.Pp
Arugment
.Fa instructions
should point to an array of frame instruction bytes, as
returned by the functions
.Xr dwarf_get_cie_info 3
or
.Xr dwarf_get_fde_instr_bytes 3 .
.Pp
Argument
.Fa len
should specify the number of the frame instruction bytes to be
translated.
.Pp
Argument
.Fa ret_ops
should point to a location that will be set to a pointer to
an array of translated
.Vt Dwarf_Frame_Op
descriptors.
.Pp
Argument
.Fa ret_opcnt
should point to a location that will hold the total number of the
returned descriptors.
.Pp
If argument
.Fa err
is not
.Dv NULL ,
it will be used to store error information in case of an error.
.Ss Memory Management
The memory area used for the descriptor array returned in argument
.Fa ret_ops
is allocated by
.Lb libdwarf .
Application code should use function
.Xr dwarf_dealloc 3
with type
.Dv DW_DLA_FRAME_BLOCK
to free the memory area when the descriptor array is no longer needed.
.Sh RETURN VALUES
Function
.Fn dwarf_expand_frame_instructions
returns
.Dv DW_DLV_OK
when it succeeds.
In case of an error, it returns
.Dv DW_DLV_ERROR
and sets the argument
.Fa err .
.Sh EXAMPLES
To retrieve and expand the frame instructions for a given FDE
descriptor, use:
.Bd -literal -offset indent
Dwarf_Dbg dbg;
Dwarf_Cie cie;
Dwarf_Fde fde;
Dwarf_Ptr fde_inst;
Dwarf_Unsigned fde_instlen;
Dwarf_Frame_Op *ops;
Dwarf_Signed opcnt;
Dwarf_Error de;

/* ... assuming `dbg` references a valid DWARF debugging context,
  `fde` references a valid FDE descriptor and `cie` holds the CIE
  descriptor associated with the FDE descriptor ... */

if (dwarf_get_fde_instr_bytes(fde, &fde_inst, &fde_instlen,
    &de) != DW_DLV_OK)
	errx(EXIT_FAILURE, "dwarf_get_fde_instr_bytes failed: %s",
	    dwarf_errmsg(de));

if (dwarf_expand_frame_instructions(cie, fde_inst, fde_instlen,
    &ops, &opcnt, &de) != DW_DLV_OK)
	errx(EXIT_FAILURE,
	    "dwarf_expand_frame_instructions failed: %s",
	    dwarf_errmsg(de));

for (i = 0; i < opcnt; i++) {
	/* ... use ops[i] ... */
}

/* Free the memory area when no longer needed. */
dwarf_dealloc(dbg, ops, DW_DLA_FRAME_BLOCK);
.Ed
.Sh ERRORS
Function
.Fn dwarf_expand_frame_instructions
can fail with:
.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Fa cie ,
.Fa instructions ,
.Fa ret_ops
or
.Fa ret_opcnt
was
.Dv NULL .
.It Bq Er DW_DLE_ARGUMENT
Argument
.Fa len
was 0.
.It Bq Er DW_DLE_MEMORY
An out of memory condition was encountered during the execution of
this function.
.It Bq Er DW_DLE_FRAME_INSTR_EXEC_ERROR
An unknown instruction was found in the instruction bytes provided
in argument
.Fa instructions .
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_frame_instructions_dealloc 3 ,
.Xr dwarf_get_cie_index 3 ,
.Xr dwarf_get_cie_info 3 ,
.Xr dwarf_get_cie_of_fde 3 ,
.Xr dwarf_get_fde_at_pc 3 ,
.Xr dwarf_get_fde_info_for_all_regs 3 ,
.Xr dwarf_get_fde_info_for_all_regs3 3 ,
.Xr dwarf_get_fde_info_for_cfa_reg3 3 ,
.Xr dwarf_get_fde_info_for_reg 3 ,
.Xr dwarf_get_fde_info_for_reg3 3 ,
.Xr dwarf_get_fde_instr_bytes 3 ,
.Xr dwarf_get_fde_list 3 ,
.Xr dwarf_get_fde_list_eh 3 ,
.Xr dwarf_get_fde_n 3
